It is commonly known in the construction industry to create spaces or voids in or under various types of concrete formations. For example, concrete formations below grade such as the structural foundation of a building often require a space or void between the foundation and the ground to accommodate expansion of the soil, thereby preventing damage to the foundation. Thus, it is often desirable to create a void between the structural floor and/or grade beams of a foundation and the underlying soil to accommodate upheaval of the soil. It may also be desirable to create a void between the walls of a foundation and the surrounding soil to accommodate a similar expansion of the soil below grade. In addition, voids can also be utilized above grade between cement floor slabs to reduce the amount of cement required and to make the resulting slab lighter.
Another type of concrete formation that sometimes requires a void is a concrete pillar or column. It is often desirable to create a void in a pillar or column to allow room for internal plumbing, electrical conduits or the like within the column. By forming a void in the column, the items within the column are protected and the cost of making the column can be reduced because less concrete is required.
Typically, these voids are created by placing a biodegradable support structure made of corrugated cardboard in the desired location. These support structures are configured to support the building structural components until the poured concrete is capable of holding its own weight. As the concrete dries, and as the cardboard eventually deteriorates, a void is left in the concrete formation. However, such support structures are typically difficult to assemble and often can only be assembled at a factory and transported to a construction site.
Support structures featuring a main wrapping sheet with separate individual insert sections have been known. While these support structures could be assembled at the construction site, they provided an unsatisfactory compressive strength. Of the many features which in combination provided the overall compressive strength, FIG. 7 shows the prior art triangular shaped peaks that served as interior supports for the support structure side walls (see dashed line 54' in FIG. 7). Such triangular peaks offered low compressive strength and thus adversely effected the quantity of concrete that could be supported by the support structure.
Another feature of the prior art structure included interior walls assembled from single sections of paperboard. The paperboard sections were folded to provide double thickness walls and single thickness walls.
Heretofore known support structures that could be assembled on site also featured ends that were open. This proved undesirable as it provided the very ends of the support structure surfaces with little or no support. In addition, such an arrangement provided an additional possible entry point for wet concrete. This was very undesirable as when the interior cardboard became wet, it lost virtually all of its strength.
Accordingly, it is an object of the present invention to provide a box-like structure that may be either delivered factory assembled to the construction site, or delivered in a "knocked-down" configuration for easy assembly and installation on site.
It is another object of the present invention to provide a box-like structure with a high compressive strength.
It is another object of the present invention to provide a box-like structure that prevents the leakage of liquid concrete into its interior.
It is still another object of the present invention to provide a box-like structure that is capable of being assembled in an efficient manner.